UNIX for Beginners Questions & Answers

We are using Solaris 11 Logical Domains. We NFS share a disk backup area from one LDom to other servers. The share is on a single 1.5 Tb LUN presented to the Control Domain, and as a virtual disk on the NFS server LDom. A 1.5 Tb zpool has been created on the LDom. We now need to provide more disk backup capacity, It needs to increase to 5.5 TB. My question is: Is it better to increase the size of this LUN to 5.5 Tb or to have a second or multiple smaller LUNS?

Your question arises out of a fairly common scenario. Many sysadmins on this forum will have experienced such a thing and you may receive different answers. What I would say from my long experience is this.

If you are backing up over NFS (which is a very common thing to do and nothing wrong with that) then the bottleneck will be the network speed not the disk interface. Backup jobs have a habit of getting bigger over time and if you have to look at several volumes to find the necessary space, it makes things much more complicated to manage. Therefore, I would say that one big volume is much easier to manage because you can see what's on it all in one go, (and decide what old backups to delete to make room).

I would suggest that, if necessary, review your network interface speed and possibly upgrade and/or aggregate/team network interfaces to up the bandwidth.

Hope that helps. Let's see what others on here think.

If you are using FC disks for that NFS server, i would advise using multiple luns.
Just add additional 3 x 1.5 TB, making it 4 x 1.5 TB zpool

ZFS will stripe the load (it's raid0 basically) across all disks in zpool.

With one monster lun you could hit queue depth problems.
One lun has final queue depth on storage side, afaik, regardless of the manufacturer.

On Solaris 11 the default queue depth is 256, which seems quite high for default, but applicable under some loads.

This won't be so noticeable on SSD or FMC modules, but doubtful you are using those for backups via NFS.
So i would go multiple luns same size as the first one you added in your situation.

Hope that helps
Regards
Peasant.